Vocabulary
Define kinetic energy.
The energy of motion.
True or False: A thermal insulator is a material which thermal energy moves slowly.
True or False: Convection currents can form in solids.
False. Convection currents can only be formed in fluids. Matter needs to flow in order to form a convection current.
Define thermodynamics.
Thermodynamics is the study of the relationships among thermal energy, heat and work.
Name two ways to increase the temperature of a system.
One way is to heat that system. Another way is to do work on that system.
Define heat.
The transfer of thermal energy.
Explain why water can be used as a coolant in a car's radiator. Can it be used in cold climates? Why?
Water has a high specific heat for a fluid, meaning it can absorb more thermal energy without a change in temperature.
It can't be used as a coolant in colder climates due to the fact that water freezes at 0°C. Also water expands when it freezes.
Define temperature.
Temperature is the measure of the average kinetic energy of the particles that make up that object.
What is the difference between passive solar heating and active solar heating?
Passive solar heating - In passive solar heating systems, materials inside a building absorb radiant energy from the Sun and heat up during the day. At night, when the building begins to cool, thermal energy absorbed by these materials helps keep the rooms warm.
Active solar heating - In active solar heating, a solar collector is used. A solar collector is a device that transforms radiant energy from the Sun into thermal energy. Radiation from the Sun heats air or water in the solar collector. A pump circulates the hot fluid to radiators in rooms of the house. Both passive solar heating and active solar heating.
Heat spontaneously moves from a warmer region to a colder region. What does spontaneous mean in this situation?
It means that the process occurs without any input of energy or work.
Define radiation.
Radiation is the transfer of energy by electromagnetic waves, such as light and microwaves.
Is conduction better in solids, liquids or gases?
Conduction is faster in solids and liquids than in gases. In gases, particles are farther apart. Therefore, collisions among particles occur less frequently in gases.
Define specific heat.
The specific heat of a material is the amount of heat need to raise the temperature of 1 kilogram of that material by 1 degree Celsius. Scientists measure specific heat in joules per kilogram degree of Celsius of that material by [ J/(kg ∙ °C) ].
State the second law of thermodynamics.
The second law of thermodynamics states that energy spontaneously spreads from regions of higher concentration to regions of lower concentration.
How do heat engines produce thermal energy to do work?
A car’s engine converts chemical energy in gasoline into thermal energy.
Chemical energy gets converted into thermal energy during combustion that occurs in the cylinders of an engine.
Define heat engine.
A heat engine is a device that converts some thermal energy into mechanical energy.
Does a hot coffee cup have a higher or lower thermal energy than a pool of water?
The pool of water has a higher thermal energy, because it has more mass. It has more particles, meaning more energy.
What is the difference between and isolated system and a non-isolated system?
A system is isolated if there are no energy transfers between that system and its surroundings. The total energy of an isolated system cannot change.
A system is non-isolated if energy is transferred between the system and its surroundings. For example, a pan on a hot stove is a non-isolated system. This means that the total energy of a non-isolated system can change.
State the formula used to calculate the thermal energy of a system? What does each variable represent.
q = thermal energy
m = mass
Tf - Ti = change in temperature
c = specific heat
How does a refrigerator cool the food inside?
A refrigerator does work as it transfers thermal energy from inside the cool refrigerator to the warmer room. The energy to do the work comes from electrical energy the refrigerator obtains from an electrical outlet. A refrigerator makes the room that it is in warmer.
Define convection
Convection is the transfer of thermal energy in a fluid by the movements of warmer and cooler fluids.
Explain why convection currents form.
Most substances expand as their temperature increases. That is, as the particles move faster, they tend to be farther apart. Recall that density is the mass of a material divided by its volume. When a fluid expands, its volume increases, but its mass does not change. Therefore, a fluid’s density decreases when that fluid is hated.
A wooden block has a mass of 0.200 kg, has a specific heat of 710 J/(kg ∙ °C), and is at a temperature of 20.0°C. What is the block’s final temperature if its thermal energy increased by 2130 J?
35°C
Calculate the specific heat of 6.4kg of a metal that has 1.67x104J of thermal energy after being heated from 25°C to 37°C .
217.4 J/(kg ∙ °C)
Explain how can a heat pump warm a house if the temperature outside is below freezing temperatures?
A heat pump can warm a house even when the temperature outside is below freezing temperatures by using a refrigerant to transfer heat from the environment to the house. The refrigerant just has to be colder than the temperature outside. This way heat gets transferred to the refrigerant, using the second law of thermodynamics.